The present invention relates to a biologically enriched substrate, a process for its preparation and its applications to the reclamation of pioneer vegetations.
The problem of the recreation of natural vegetation is becoming increasingly urgent in view of the slow and progressive disappearance of certain media on the scale of a country or even a continent, which makes it imperative to preserve the biocenoses.
It has thus become necessary to recreate natural vegetations in order to restore the initial vegetations that have been dislocated.
There is further observed the reduction of the quality and genetic potential provided by undomesticated wild flora; certain vegetables disappear within the biocenosis; vegetables that could have contributed to the preparation of medicines or to the future food supply or could have been used to improve certain useful plants, whether they are edible, medical or intended for industrial applications.
There are at present numerous processes in existence for the reconstitution of the disturbed phytoecological environment; however, an examination of the different solutions proposed on a world scale has lead the present inventors to conclude that no satisfactory solution has been found; whether to stabilize the sites or to plant pioneer vegetable species.
Operations of the hydraulic sowing of grass seeds into a bare inorganic soil represent at this time one of the most frequently used reclaiming processes. The seeds are initially mixed with water, fertilizers and with substances intended to physically and chemically improve the soil and with adhesive substances (alginates, cellulose derivatives, latex . . . ).
These hydraulic sowing operations do not always lead to positive results. This occurs in particular when the soil is unstable (sand, clay . . . ), in cases where abnormal dryness rises above a certain threshold (pronounced seasonal extreme dryness leading to extensive withering in the summer), also in the case of seasonal thermophilia not suitable for artificially introduced species. On the other hand, certain substrates are unstable; the coverings applied (simple deposition of an alginate, cellulose, or latex film) are fragile and in the case of abundant rain the seeds are carried away prior to their sprouting.
Finally, these methods use large quantities of fertilizers, essentially nitrogen fertilizers, in order to try to obtain in the first year good development of the seedings. But the damage caused to the environment by nitrogen fertilizers is well known at the present time, in particular due to the presence of nitrates in the phreatic layers.
Furthermore, hydraulic seeding operations are anthropic and artificial formations which cannot merge into a natural landscape.
In certain cases of conventional hydraulic seeding, partial successes are achieved, because certain plants introduced in the form of grains are well adapted. However, in this case genetic pollution occurs and there is a risk for the indigenous flora of competition for sites; in numerous cases the plant introduced prevails.
As an example, Erigon canadensis, a weed which appeared at the turn of the century in France, or Elodea canadensis, the growth of which interfered with traffic on canals in canals in England around 1930, may be mentioned. Bacharis halimifolia may also be cited; following its use in gardens it is about to become a plague for atlantic salt marshes or the bottom of Northern Portugal, introduced on the borders of freeways and hindering the growth of the broom (Sarothamus scoparius).
It is found in effect that the plants introduced do not always adapt, with the result that they regress more or less slowly. The soil becomes more or less destablized or it recolonizes naturally, but, depending on the data of the thermoxerophilic character of the medium seeded, regression may last for 2 to 10 years and as a function of the particular case, it may take 5 to 25 years to develop natural recolonization. However, in the latter case the natural species of the recolonization will be less numerous due to the isolation of the sites relative to identical natural environments (diaspora reservoir).
It thus became necessary to resolve both the technical problem of stabilization and that of the reconstitution of plants.
The phenomenon of the colonization of soils follows an identical scheme at all latitudes and in all climates; it is more or less rapid or partial depending on the degree of dryness or the nature of erosion.
This scheme, which remains the same on the plains, at the seashore and in the mountains up to 3000 m, has succeeded in forming on our planet over approximately 400 million years the luxuriant vegetation that we know. It may for example be summarized as follows in an acid medium:
Stage 1: bare and infertile soil PA1 Stage 2: essentially consisting of Cyanophycea (blue algae)--0.5 mm organic matter; 4 to 10 species or more, depending on the site, PA1 Stage 3: Bryophytes (mosses)--5 to 25 mm of organic matter--moder type; 3 to 6 species or more, depending site, PA1 Stage 4: Therophyte pre-sod (Bryophytes and annual plants)--high productivity of organic matter--thickness 25-70 mm--moder type; pre-sod in a phytosociology of the following classes: Festco-Brometea, Lygeo-Stipetea, Sedo-Scleranthetea, Poetea-bulbosae, Tuberarietea, PA1 Stage 5: Turf with Graminea dominating--organic matter in accumulation; thickness 60-300 mm--moder then ranker type. PA1 an alpine medium: the flora of the moraines and the flora of rubble also found in abyssals in the flood paths where the instability of their moraine or rubble is again present in the gravel; PA1 in an environment of plains, plants of rubble or of overturned soil are frequently found in certain cultivated soils: Example. Tussilago-farfara in the vines. PA1 in a maritime environment it is the flora of the mobile dunes.
All of these stages are necessary for the creation of humus (mull or moder), which constitutes the beginning of the evolution of the soils toward rankers in co-evolution with the implantation of the sod stage. It is known that it required 2000 to 3000 years to obtain alpine or atlantic rankers.
It is necessary to wait 5 to 20 years in an unstable thermo-xerophilic situation to see the first Byrophytes occupy the degraded soil. Depending on the degree of dryness; between 10 and 30 years are required to obtain a sufficiently thick soil to permit the installation of the sod.